With the introduction into IS-2000 CDMA systems of technologies such as smart antenna and Selectable Mode Vocoder (SMV), Walsh code availability has become an important system capacity issue. For example, with only 64 Walsh codes per sector, Radio Configuration (RC) 3 is Walsh code limited for the SMV and smart antenna features. One way to solve this Walsh code availability problem is to use RC4. However, RC4's capability of doubling the number of available Walsh codes is achieved at the expense of RF capacity. In fact, simulation has shown that compared to an RC3 voice call, an RC4 call would require a 1.15 dB higher signal-to-noise ratio (SNR) to achieve the same frame error rate (FER). Thus, using RC4 can lead to more than a 20% reduction in RF capacity.
The prior art proposes methods for using RC3 and RC4 together to manage the Walsh code availability in a system, but these methods effectively trade RF capacity to obtain additional Walsh codes. However, if a system is both Walsh code limited and near its RF capacity limits, these techniques can not be used. There is no RF capacity left to trade for more Walsh codes. Therefore, a need exists for a new apparatus and method that provides additional Walsh codes without trading off RF capacity.